Aqueous coatings may be used to coat the inside of containers to meet various end use application requirements. For example, coatings used in containers for beer and beverages or other sanitary cans should meet strict requirements such as adhesion, boiling water tests, retorting, blush resistance and the like. To meet these requirements, most container coatings utilize curing resins. These curing resins, such as melamine formaldehyde polymers and others, release volatile organic compounds (VOCs) into the atmosphere during baking cycles. These VOCs are in addition to the solvents normally measured for VOC determination that are often used in aqueous coatings to promote substrate wetting, flow properties, etc.
Several attempts have been made to formulate coatings that do not introduce high levels of VOCs into the environment during curing. Unfortunately, however, most of these attempts result in unsatisfactorily coated products. For example, the removal or reduction of VOCs by vacuum stripping the aqueous solution has resulted in blisters or non-uniformly coated substrates.
From the foregoing, it will be appreciated that what is needed in the art is a coating composition that has reduced VOC content, and the ability to produce coated containers satisfactory to meet end oftentimes stringent use requirements.